Recently I put on a tape of the Coltrane quartet in my car and caught the middle of this tune where there was this far-out dialogue between Trane and Elvin Jones. I was thinking, what the hell are they doing? A minute or two later it became clear: They were playing the blues. They had really abstracted the form, but then they landed where it was really coming from. There's something powerful in hearing that grounding come through. It's not possible to understand that very abstract stuff without understanding a basic blues.